| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20251125175753.1428857-5-prsampat@amd.com>
Date: Tue, 25 Nov 2025 11:57:53 -0600
From: "Pratik R. Sampat" <prsampat@....com>
To: <linux-mm@...ck.org>, <linux-coco@...ts.linux.dev>,
<linux-efi@...r.kernel.org>, <x86@...nel.org>, <linux-kernel@...r.kernel.org>
CC: <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
<dave.hansen@...ux.intel.com>, <kas@...nel.org>, <ardb@...nel.org>,
<akpm@...ux-foundation.org>, <david@...hat.com>, <osalvador@...e.de>,
<thomas.lendacky@....com>, <michael.roth@....com>, <prsampat@....com>
Subject: [RFC PATCH 4/4] mm: Add support for unaccepted memory hot-remove
Transition memory to shared during a hot-remove operation so that it can
be re-used by the hypervisor. During lazy acceptance, only memory that
was used has been accepted, therefore during hot-remove only mark pages
as shared that were previously accepted / made private.
Signed-off-by: Pratik R. Sampat <prsampat@....com>
---
arch/x86/coco/sev/core.c | 23 +++++++++++++++
arch/x86/include/asm/sev.h | 2 ++
arch/x86/include/asm/unaccepted_memory.h | 9 ++++++
drivers/firmware/efi/unaccepted_memory.c | 37 ++++++++++++++++++++++++
include/linux/mm.h | 7 +++++
mm/memory_hotplug.c | 2 ++
6 files changed, 80 insertions(+)
diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index a5c9615a6e0c..c05fc91d10a1 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -621,6 +621,29 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end)
set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE, 0);
}
+void snp_unaccept_memory(phys_addr_t start, phys_addr_t end)
+{
+ unsigned long vaddr, npages;
+
+ if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+ return;
+
+ vaddr = (unsigned long)__va(start);
+ npages = (end - start) >> PAGE_SHIFT;
+
+ /*
+ * Hotplugged memory can be set to shared externally. Attempting to
+ * re-share the memory (during hot-remove) will cause the pvalidate
+ * operation to not make any changes to the RMP table triggering the
+ * PVALIDATE_FAIL_NOUPDATE condition
+ *
+ * Since the memory hotplug case is unique, specify this intent so that
+ * if the page is part of hotplugged memory a pvalidate rescind
+ * operation is not performed
+ */
+ set_pages_state(vaddr, npages, SNP_PAGE_STATE_SHARED, SNP_PSC_SHARED_TO_SHARED);
+}
+
int snp_extend_hotplug_memory_state_bitmap(phys_addr_t start,
unsigned long size,
uint64_t unit_size)
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index eb605892645c..8f3c5b878fd7 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -547,6 +547,7 @@ void __noreturn snp_abort(void);
void snp_dmi_setup(void);
int snp_issue_svsm_attest_req(u64 call_id, struct svsm_call *call, struct svsm_attest_call *input);
void snp_accept_memory(phys_addr_t start, phys_addr_t end);
+void snp_unaccept_memory(phys_addr_t start, phys_addr_t end);
u64 snp_get_unsupported_features(u64 status);
u64 sev_get_status(void);
void sev_show_status(void);
@@ -639,6 +640,7 @@ static inline int snp_issue_svsm_attest_req(u64 call_id, struct svsm_call *call,
return -ENOTTY;
}
static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
+static inline void snp_unaccept_memory(phys_addr_t start, phys_addr_t end) { }
static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
static inline u64 sev_get_status(void) { return 0; }
static inline void sev_show_status(void) { }
diff --git a/arch/x86/include/asm/unaccepted_memory.h b/arch/x86/include/asm/unaccepted_memory.h
index abdf5472de9e..ad392294b71b 100644
--- a/arch/x86/include/asm/unaccepted_memory.h
+++ b/arch/x86/include/asm/unaccepted_memory.h
@@ -18,6 +18,15 @@ static inline void arch_accept_memory(phys_addr_t start, phys_addr_t end)
}
}
+static inline void arch_unaccept_memory(phys_addr_t start, phys_addr_t end)
+{
+ if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) {
+ snp_unaccept_memory(start, end);
+ } else {
+ panic("Cannot accept memory: unknown platform\n");
+ }
+}
+
static inline struct efi_unaccepted_memory *efi_get_unaccepted_table(void)
{
if (efi.unaccepted == EFI_INVALID_TABLE_ADDR)
diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
index 6796042a64aa..662cf0d6715f 100644
--- a/drivers/firmware/efi/unaccepted_memory.c
+++ b/drivers/firmware/efi/unaccepted_memory.c
@@ -301,6 +301,43 @@ int accept_hotplug_memory(phys_addr_t mem_range_start, unsigned long mem_range_s
return 0;
}
+void unaccept_hotplug_memory(phys_addr_t mem_range_start, unsigned long mem_range_size)
+{
+ u64 unit_size, phys_base, bit_start, bit_end, addr;
+ struct efi_unaccepted_memory *unacc_tbl;
+ unsigned long flags, *bitmap;
+ phys_addr_t start, end;
+ int i;
+
+ unacc_tbl = efi_get_unaccepted_table();
+ if (!unacc_tbl)
+ return;
+
+ phys_base = unacc_tbl->phys_base;
+ unit_size = unacc_tbl->unit_size;
+
+ start = mem_range_start - phys_base;
+ end = (mem_range_start + mem_range_size) - phys_base;
+
+ bit_start = start / unit_size;
+ bit_end = end / unit_size;
+
+ /* Only unaccept memory that was previously accepted in the range */
+ for (i = bit_start; i < bit_end; i++) {
+ spin_lock_irqsave(&unaccepted_memory_lock, flags);
+ bitmap = efi_get_unaccepted_bitmap();
+ if (!bitmap || test_bit(i, bitmap)) {
+ spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
+ continue;
+ }
+
+ addr = phys_base + i * unit_size;
+
+ arch_unaccept_memory(addr, addr + unit_size);
+ spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
+ }
+}
+
#ifdef CONFIG_PROC_VMCORE
static bool unaccepted_memory_vmcore_pfn_is_ram(struct vmcore_cb *cb,
unsigned long pfn)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index bb43876e6c47..34d48693dc86 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4079,6 +4079,8 @@ bool range_contains_unaccepted_memory(phys_addr_t start, unsigned long size);
void accept_memory(phys_addr_t start, unsigned long size);
int accept_hotplug_memory(phys_addr_t mem_range_start,
unsigned long mem_range_size);
+void unaccept_hotplug_memory(phys_addr_t mem_range_start,
+ unsigned long mem_range_size);
bool mm_lazy_accept_enabled(void);
#else
@@ -4099,6 +4101,11 @@ static inline int accept_hotplug_memory(phys_addr_t mem_range_start,
return 0;
}
+static inline void unaccept_hotplug_memory(phys_addr_t mem_range_start,
+ unsigned long mem_range_size)
+{
+}
+
static inline bool mm_lazy_accept_enabled(void) { return false; }
#endif
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index bf8086682b66..0b14b14e53fe 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -2254,6 +2254,8 @@ static int try_remove_memory(u64 start, u64 size)
mem_hotplug_begin();
+ unaccept_hotplug_memory(start, size);
+
rc = memory_blocks_have_altmaps(start, size);
if (rc < 0) {
mem_hotplug_done();
--
2.51.1
Powered by blists - more mailing lists